1. Technical Field
The invention relates to an oil recovery process and more particularly to a process of placing an acrylamide polymer gel in a high-temperature formation for oil recovery applications.
2. Description of Related Art
Polymer gels have potential application to a number of processes designed to improve oil recovery formations. Such processes include conformance improvement, cementing, and fracturing. Conformance improvement can be necessary when one is flooding or producing a formation exhibiting poor vertical or areal conformance. Poor vertical conformance results from the vertical juxtaposition of relatively high permeability geologic regions to relatively low permeability regions within a substerranean fromation. Poor areal conformance results from the presence of high permeability streaks and high permeability anomalies within the formation matrix, such as vertical fractures and networks of the same, which have very high permability relative to the formation matrix.
Fluids generally exhibit poor flow profiles and sweep efficiencies in subterranean formations having poor vertical or areal conformance. Poor conformance is particularly a problem where vertical heterogeneity, fracture networks or other structural anomalies are in fluid communication with a subterranean wellbore across which fluids are injected or produced.
A number of attempts to remedy conformance problems exist. U.S. Pat. Nos. 3,762,476; 3,981,363; 4,018,286; and 4,039,029 to Gall or Gall et al describe various processes wherein crosslinked polymer gel compositions are formed from gelation systems in high permeability regions of subterranean formations to reduce the permeability therein. However, in practice, prior art conformance treatments employing in situ gelation have proven unsatisfactory because the gelation systems are extremely difficult to regulate once the system is injected into a formation.
Controlling the gelation reaction is a particularly acute problem in high-temperature formations because the high temperatures can induce excessive gelation of the system as soon as it contacts the formation. As a result, the gel sets up before it can sufficiently penetrate the treatment region and the region does not achieve uniform permeability reduction. This effect diminishes the degree of conformance improvement which one can realize with conventional gel treatments in high-temperature formations.
A need exists for a gelation process wherein a gelation system gels in situ at a slow, controlled rate, even at high formation temperatures. A need exists for a process wherein a gelation system substantially delays geletion until it has effectively penetrated the desired treatment region of a subterranean hydrocarbon-bearing formation at which time the system sets up as a uniform immobile gel.